Water-miscible Liquids Research Articles

Liquid concentration sensing via weakly coupled point defects in a phononic crystal

A pair of weakly coupled point defects in a liquid–solid phononic crystal are employed for liquid concentration sensing. An exemplary case of methanol in ethanol is investigated. As the physical and chemical properties of the two constituents are very similar, sensing is a rather difficult task by other analytical means. The defects are formed by thin-walled polyethylene tubing filled with either the reference liquid (ethanol) or the mixture in a square phononic crystal composed of cylindrical steel rods in water. Finite-element method simulations for the dual defect system, which has a small form factor comparable to the acoustic wavelength in water, revealed that two sharp transmission peaks corresponding to the even and odd modes arising from symmetry lifting due to weak defect interaction behave in different manners as the methanol concentration is varied. Specifically, the even mode frequency exhibits a linear dependence on the concentration, whereas the odd mode is associated with a quadratic shift. Besides, a simple coupled mass-spring model is employed to analyze the observed peak behavior as a function of methanol concentration in ethanol. Accordingly, when the acoustic properties of the two liquids in a binary mixture vary in a parallel manner with temperature, the ratio of the resonance frequencies depends only on the concentration, thus offering a sensing scheme immune to temperature fluctuations. Furthermore, it is shown for a number of water-miscible liquids that the even and odd mode frequencies are representative of the dominant contents of the reference and the sample cells.

Mechanism of pore wetting in membrane distillation with alcohol vs. surfactant

Pore wetting is a unique and important technical challenge that can lead to process failure in membrane distillation (MD) using hydrophobic membranes. While it is well known that both low-surface-tension and water miscible liquids, such as alcohols, and amphiphilic molecules, such as surfactants, are effective wetting agents, the detailed mechanisms for these agents to induce pore wetting remain unclear. In particular, the role of surface adsorption in surfactant-induced wetting remains to be elucidated. This study provides fundamental insights to understanding the mechanism of pore wetting induced by these two different wetting agents. Using a recently developed wetting monitoring technique based on single-frequency transmembrane impedance, we experimentally probe the kinetics of wetting frontier propagation. We demonstrate that ethanol-induced wetting is instantaneous whereas surfactant-induced wetting is dynamic with its kinetic rate dependent on several critical factors. We also develop a theoretical model, based on the assumption of quasi-equilibrium adsorption, to successfully explain the important features experimentally observed in surfactant-induced wetting. Specifically, it was found that the kinetics of surfactant-induced wetting strongly depends on the vapor flux and the bulk concentration of surfactants in the feed solution, but surprisingly not on the transmembrane hydraulic pressure difference. The results from our study also suggest that while the presence of surfactants promotes wetting, adsorption of surfactants onto pore surface actually deters pore wetting instead of promoting it by rendering the surface hydrophilic.

Modeling heat transport in nanofluids with stagnation point flow using fractional calculus

This paper studies the flow and heat transfer of power-law type nanofluids with stagnation point flow past a porous sheet. The governing equation of temperature involving spatial fractional derivative is used to investigate the anomalous heat diffusion of nanofluids. Four types of nanoparticles are considered with the carboxymethyl cellulose and water miscible liquids as the heat transfer fluid. By suitable similarity transformations, the governing partial differential equations are reduced to a system of ordinary differential equations, which are discussed thoroughly. It is found that the thermal transfer ability of nanofluids shows inverse correlation with the order of fractional derivative. Effects of the other physical parameters on flow and heat transfer are analyzed in detail.

Preparation and Characterization of Stable Aqueous Ferrofluids Using Low Molecular Weight Sulfonated Polystyrene

AbstractSummary: One of the most optically transparent magnetic materials known at room temperature consists of nanocrystalline γ‐Fe2O3 dispersed in a DVB cross‐linked sulfonated polystyrene (PS) matrix. When attrited dry or in water without surfactant and subsequently processed in water or water miscible liquids, the nanocomposite leads to a highly stable, low optical density ferrofluid with unique properties and uses in a variety of applications. We have heretofore identified the stabilizing agent in the ferrofluid as low molecular weight (∼6000) sulfonated PS, which results from attrition of the cross linked polystyrene nanocomposite. We report on the synthesis of low molecular weight (LMW) PS by atom transfer radical polymerization (ATRP) followed by sulfonation with acetyl sulfate and on the one‐step synthesis of a stable ferrofluid of nanocrystalline Fe3O4 using the newly synthesized LMW sulfonated PS. Physicochemical analyses and characterizations include GPC, GC‐MS, GPC, NMR, FTIR, XRD, TEM and magnetic data.

Ether-Functionalized Imidazolium Hexafluorophosphate Ionic Liquids for Improved Water Miscibilities

The hexafluorophosphate anion of 1-alkyl-3-methylimidazolium ionic liquids is responsible for their poor water miscibility. Transformation of the hexafluorophosphate ionic liquids into water miscible liquids by structural modifications in the imidazolium cation could result in new applications. Improved water miscibilities were achieved with 1-alkyl ether-3-methylimidazolium hexafluorophosphate ionic liquids. Especially, ionic liquid 1-triethylene glycol monomethyl ether-3-methylimidazolium hexafluorophosphate 5 showed a strongly increased water miscibility range at 30 °C, which was further enhanced in the presence of ethanol as cosolvent. Besides, a complete water miscibility of 5 was observed at an elevated temperature of 50 °C. This knowledge may facilitate the predictive development of new task-specific ionic liquids.

Fire tests of rack storage of water miscible liquids in plastic containers

AbstractThis article deals with fire protection for water miscible flammable liquids stored in plastic containers packaged in boxes located on pallets. A series of fire tests was conducted with palletized rack storage arrangements using in‐rack sprinkler protection at various levels. The intent of the paper is to present data from this test series for these types of commodities. The paper will identify various existing water miscible flammable liquid products stored in this fashion and provide background information for protecting this type of storage as it relates to NFPA 30 Flammable and Combustible Liquids Code. The test data indicates that further research work is needed in the area of plastic containers for use with the storage of combustible and flammable liquids. Included in the paper are discussions concerning possible protection strategies and suggestions for future research which would benefit those involved in risk management of this type of commodity.